Switch construction for high voltage a.c. power circuits having arcing horns arranged for closing against high fault currents



Sept. 1965' .1. J. M|Kos 3,206,581

SWITCH CONSTRUCTION FOR HIGH VOLTAGE A.C- POWER CIRCUITS HAVING ARCING'HQRNS ARRANGED FOR CLOSING AGAINST HIGH FAULT CURRENTS Filed July 15,19625 :5 Sheets- Sheet 1 Sept. 14, 1965 J. J. MIKOS 3,206,581

SWITCH CONSTRUCTION FOR HIGH VOLTAGE A.C. POWER CIRCUITS HAVING ARCINGHORNS ARRANGED FOR CLOSING AGAINST HIGH FAULT CURRENTS Filed July 15,1965 5 Sheets- Sheet 2 Sept. 14, 1965 os SWITCH CONSTRUCTION FOR HIGHVOLTAGE A.c. POWER CIRCUITS HAVING ARcING HORNS ARRANGED FOR cLOsINGAGAINST HIGH FAULT GURRENTS 3 Sheets-Sheet 3 Filed July 15, 1965 UnitedStates Patent SWITCH CONSTRUCTION FOR HIGH VOLTAGE A.C. POWER CIRCUITSHAVING ARCIN G HORNS ARRANGED FOR CLOSING AGAINST HIGH FAULT CURRENTSJohn J. Mikos, Highland Park, Ill., assignor to S & C Electric Company,Chicago, Ill., a corporation of Delaware Fiied July 15, 1963, Ser. No.294,845 Claims. (Cl. 200-146) This invention relates, generally, tocircuit makers and breakers, and it has particularly relation to theconstruction of switches for the use on high voltage alternating currentpower circuits operating at voltages of the order of 138 kv. Itconstitutes an improvement over the com structions shown in US. PatentNo. 2,894,101, issued July 7, 1959, to S. I. Lindell et al. and No.3,030,481, issued April 17, 1962, to W. A. Gussow et al.

Among the objects of this invention are: To provide a relativelystationary switch contact construction for engagement by a disconnectingswitch blade that is capable of withstanding the stresses incident toclosing the switch blade against fault currents of relatively greatmagnitude, for example fault currents of the order of 40,000 to 50,000crest amperes; to arrange the contact construction in such a manner thatit can be employed on circuits operating at 138 kv. or higher withoutrequiring the use of special devices, such as corona balls, to avoid theeffects of corona discharge; to employ for this purpose a pair of arcinghorns arranged to maintain contact with the switch blade in a new andimproved manner prior to its engagement with the relatively stationaryswitch contact and immediately after its disengagement therefrom; toconstruct each arcing horn of rod-like resilient material in an invertedU-shape or hair pin shape with one arm shorter 1 than the other forengagement with one side of an arcing tip extending endwise from theswitch blade, the arcing horns being located on opposite sides of thearcing tip and the distal ends of the shorter arms being freely movablewith respect to each other; to attach the longer arms of the invertedU-shaped arcing horns to the base of the stationary switch contact toposition the shorter arms in staggered relation on opposite sides of thecontact tip when the switch blade is closed; to interconnect rigidly thelonger arms of the inverted Ushaped arcing horns at a location wellabove their attachment to the base of the stationary switch contact andbelow the distal ends of the shorter arms; to employ a tie bar formaking the rigid interconnection between the longer arms of the arcinghorns; to position the inverted U-shaped arcing horns such that, whenthe switch blade is in the open position, the shorter arms extend toopposite sides of the path of the arcing tip in moving to the switchclosed position; to limit the movement of the switch blade in theclosing direction such that the arcing tip is not moved to a positionbelow the distal ends of the shorter arms of the inverted U-shapedarcing horns; to locate the bight of the arcing horn nearer the axis ofrotation of the switch blade above the arcuate path of the distal end ofthe arcing tip; and to arrange the coextentsive portions of the arms ofeach arcing horn in generally parallel relation and in planesintersecting the arcing tip generally at right angles.

In the drawings:

FIG. 1 is a view, in side elevation, of a switch construction providedwith a stationary switch contact embodying the present invention.

FIG. 2 is a view, at an enlarged scale, of the stationary contactconstruction, the view being taken looking from right to left in FIG. 1with the switch blade out of contact engagement with the stationaryswitch contact.

Patented Sept. 14, 1965 FIG. 3 is a view, similar to FIG. 2, but showingthe positions of the arcing horns when the arcing tip on the switchblade is located therebetween in the switch closed position FIG. 4 is aview, in side elevation, of the switch contact construction shown inFIGS. 2 and 3, certain arts being broken away in order to show thedetails of construction, and the distal end of the switch blade carryingthe arcing tip being shown in the switch closed position.

FIG. 5 is a top plan view of the construction shown in FIG. 4, only thearcing tip being shown by broken lines and certain parts being brokenaway in order to show the details of construction.

FIG. 6 is a top plan view, at an enlarged scale, of the tie bar that isemployed for rigidly interconnecting the longer arms of the arcinghorns.

FIG. 7 is a side elevational view of the tie bar shown in FIG, 6, aportion being broken away in order to show the details of construction.

Referring now particularly to FIG. 1 of the drawings, it will beobserved that the reference character 10 designates, generally, switchmeans in which the present invention is embodied. The switch means 10includes a base, indicated generally at 11, that may be formed of a pairof rolled steel channels suitably secured together. Mounted on the base11 are a first insulator 12, a second insulator 13, which is rotatable,and a third insulator 14. The second insulator 13 is rotatably mountedon a bearing 15 that is carried by the base 11 and it has an arm 16extending therefrom for connection to a suitable op erating linkage thatis indicated, generally, at 17. It will be understood that, for threephase operation, three of the switch means 10 are mounted on a suitableswitching structure in proper spaced relation, depending upon thevoltage of the circuit, and suitable operating means connected to theoperating linkage 17, is provided for effecting simultaneous rotation ofthe second insulator 13 of each switch means 10 for either opening orclosing the circuit as may be required.

Extending upwardly from and rotatable with the second insulator 13 is ashaft 18. The shaft 18 extends through and is rotatably mounted on amechanism housing 19 the details of construction of which are set forthin US. Patent No. 3,030,481 above referred to. The mechanism in themechanism housing 19 is described in detail in the patent just referredto.

The shaft 18 extends through the mechanism housing 19 and carries at itsupper end a switch crank 20 which is rotatable therewith. The switchcrank 20 is pivotally connected to a link 21 that is pivoted at 22 to anarm 23 which extends from a switch blade 24 that forms a part of adisconnecting switch, indicated generally at 25. The switch blade 24 ispivoted at 26 on a bracket 27 which is carried by one wall of themechanism housing 19. At its distal end the switch blade 24 is arrangedto move into and out of high pressure contact engagement with arelatively stationary switch contact, shown generally at 28, which iscarried by the first insulator 12. It will be understood that, onrotation of the second insulator 13 by the operating linkage 17, acorresponding rotation of the switch crank 20 is effected for swingingthe switch blade 24 out of or into high pressure contact engagement withthe relatively stationary switch contact 28, depending upon thedirection of rotation. In this operation the switch blade 24 also isrotated about its longitudinal axis as described in US. Patent No.2,818,474, issued December 31, 1957, to W. A. Gussow.

It is desirable that the switch blade 24 be opened only after thecircuit has been opened previously by some other means. The reason forthis is to prevent the drawing an arc between the distal end of theswitch blade 24 and the relatively stationary switch contact 28 when thecircuit is interrupted under load which might result in damage to theseparts or the creation of a fault by arcing over to an adjacent phase orto ground. For this purpose there is mounted between the mechanismhousing 19 and a line terminal 29 which is carried by the thirdinsulator 14, a current interrupter that is indicated, generally at 30.Preferably the current interrupter 30 is constructed as disclosed in US.application Serial No. 111,998, filed May 23, 1961, by John I. Mikos etal., now Patent No. 3,163,- 736, issued December 29, 1964. However, itwill be understood that other circuit interrupters can be employed inlieu of the particular circuit interrupter 30 just referred to.

The relatively stationary switch contact 28 is mounted on a lineterminal 32, which is carried by the first insulator 12. The presentinvention has particularly to do with improvement in the construction ofthe relatively stationary switch contact 28. More specifically itrelates to the provision and arrangement of arcing horns, to bedescribed, which facilitate the closing of the switch blade 24 againstheavy current fiow, such as the flow of fault current.

Except for the particular construction of the arcing horns, to bedescribed, the details of construction of the relatively stationaryswitch contact 28 are generally as shown in US. Patent No. 2,894,101,issued July 7, 1959, to S. I. Lindell et al. FIGS. 2, 3, 4 and 5 showthe details of construction of the relatively stationary switch contact28. It includes a jaw contact frame base 33 that may be secured by bolts34, FIG. 1, to the line terminal 32. Inverted U-shaped contact members35-35 extend upwardly from opposite sides of the frame base 33 andinclude inner downwardly extending arms 36-36 for high pressure contactengagement with ears on the switch blade 24, one of which is shown bybroken lines at 37 in FIG. 4. It will be understood that the switchblade 24 is rotated about its longitudinal axis to move the cars 37 intohigh pressure contact engagement with the inner faces of the downwardlyextending inner arms 36-36. The contact members 35-35 also include outerarms 38-38 which are reinforced by back-up springs 39-39, the assemblybeing secured by bolts 40-45 to the opposite sides of the frame base 33.The distal ends of the inner arms 36-36 have a loading pin 43 extendingtherethrough. Leaf springs 44-44, extending along the outer sides of theinner arms 36-36, bear against the outer ends of the loading pin 43 andextend underneath pins 45-45 that project transversely through anequalizer bar 46 the ends of which project beyond the back-up springs39-39 and through which loading pins 47-47 extend. As described in theLindell et al. Patent No. 2,894,101, above referred to, thisconstruction facilitates the movement of the switch blade 24 into andout of high pressure contact engagement with the switch contact 28.

With a view to cushioning the final movement of the switch blade 24 inthe switch closing direction, a blade stop plunger 48 is employed asshown in FIG. 4. The blade stop plunger 48 is slidable in the upper endof a sleeve 49 that is formed integrally with the frame base 33. At thelower portion of the sleeve 49 bumper pads 50 are inserted forresiliently cushioning the stopping of the blade plunger 48 on impactionby the switch blade 24 when it is moved to the closed position. A pin51, which extends transversely through the lower end of the blade stopplunger 48 and through an elongated slot 52 in each side of the sleeve49, limits the movement of the blade stop plunger 48 to the extentpermitted by the slots 52.

When the switch blade 24 is moved toward contact engagement with theswitch contact 28 and the circuit is to be completed against the flow offault current of relatively great magnitude, such as a flow of severalthousands of amperes, particularly severe mechanical and electricalproblems are encountered. It is conventional to employ horn gapconstructions in switches for these applications.

When they are subjected to high fault currents, magnetic forces arecreated between the moving and stationary arcing terminals which tendmechanically to blow them apart. As a result arcing is prolonged orreestablished in open air. The open arc gives rise to considerableburning of the metallic conducting parts which produces much splatter ofmetal on the main contact areas as well as erosion of the arcingterminals.

In accordance with this invention arcing horns 55-55 are employed. Theyare of generally inverted U-shape or hair pin shape as is apparent fromFIGS. 2 and 3. Preferably they are formed from resilient rod-like brassalloy conducting material having a circular cross section. For example,they may be formed of Everdur alloy. The arcing horns 55-55 includeshorter arms 56-56 that are arranged to engage opposite sides of anarcing tip 57 that extends endwise from the switch blade 24 as shownmore clearly in FIGS. 1 and 4 of the drawings. The arcing horns 55-55are mounted on the frame base 33 in staggered relation so that, as shownin FIG. 5, the shorter arms 56-56 engage opposite sides of the arcingtip 57 in a spaced apart relation rather than opposite each other. Thereason for this arrangement is to facilitate breaking loose the arcingtip 57 from the arcing horns 55-55 under icing conditions or to permitits application thereto under these conditions. The arcing horns 55-55also include downwardly extending longer arms 58-58 which are generallyparallel to the shorter arms 56-56 in the region where they arecoextensive. It will be noted that the longer arms 58-58 andconsequently the shorter arms 56-56 are inclined outwardly with theresult that the distal ends 59-59 of the shorter arms 56-56 intersect onopposite sides of a plane that is indicated by a broken line 60, thisbeing the plane of movement of the arcing tip 57 as it is rotated intoor out of the switch closed position. Preferably the angle ofinclination of the arcing horns 55-55 away from the plane 60 is of theorder of 5. The lower ends 61-61 of the longer arms 58-58 extendvertically upwardly from the frame base 33. They are positioned, asshown in FIG. 4, in staggered relation in a boss 62 that is formedintegrally with the frame base 33, and they are held in place insuitable apertures therein by set screws 63.

It will be noted that the distal ends 59-59 of the shorter arms 56-56are free of attachment and that they can move independently of eachother. However, it is desirable that, once the arcing tip 57 engages oneor the other of the shorter arms 56-56, contact engagement therewith bemaintained during the continued movement of the switch blade 24 to theswitch closed position. In order to make certain that this contactengagement is maintained, a tie bar 64 is employed for rigidlyinterconnecting the longer arms 58-58 of the arcing horns 55- 55 at aposition, shown in FIGS. 2 and 3, well above the attachment of the lowerends 61-61 to the frame base 33 and immediately below the distal ends59-59 of the shorter arms 56-56. FIGS. 6 and 7 show the details ofconstruction of the tie bar 64. Preferably it is formed of brass alloyrod, such as Everdur alloy rod, and it has inclined circular openings65-65 near its ends for receiving the outwardly inclined longer arms58-58 of the arcing horns 55-55. The ends of the tie bar 64 are providedwith threaded openings 66-66 for receiving socket head set screws 67,one of which is shown in each of FIGS. 2, 3 and 4.

By providing the tie bar 64 rigidly interconnecting the longer arms58-58 of the arcing horns 55-55, contact engagement with one or theother of the shorter arms 56-56 is made certain when the switch blade 24moves the arcing tip 57 into engagement therewith during the closingmovement. Yet the shorter arms 56-56 are free to flex independently ofeach other in order to accommodate a substantial degree of misalignmentbetween the switch blade 24 and the switch contact 28.

While the blade stop plunger 48 limits the closing movement of theswitch blade 24 such that the arcing tip 57, under normal opeartingconditions, is not moved below its position as shown in FIG. 3, there isa remote possibility that the arcing tip 57 might become positionedbetween the longer and shorter arms 56 and 58 of one or the other of thearcing horns 55-55. In FIG. 1 the broken line 68 indicates the arcuatepath of the distal end 69 of the arcing tip 57. The arcing horns 55-55extend upwardly above the frame base 33 to such a position that thebights 70-70, and particularly the bight 70 of the arcing horn 55 nearerthe pivot axis 26 of the switch blade 24 is above the arcuate pathrepresented by the broken line 68 of the distal end 69 of the arcing tip57. With this arrangement, even if the arcing tip 57 should bepositioned between the shorter and longer arms 56 and 58 of one or theother arcing horns 55-55, it could not engage the bight 70 of either ofthem and prevent the swinging of the switch blade 24 to the switch openposition. While this action is unlikely, it is possible upon closingunder excessive fault current conditions. Referring to FIG. 5, it willbe understood that the magnetic forces acting under these conditionswill tend to move the outer arcing horn 55 past the distal end of thearcing tip 57 while the inner arcing horn 55 is held against movement bythe outer end of the switch blade 24. Thus the arcing tip 57 might enterthe space between the arms 56-58 of the outer arcing horn 55. However,because the bight 70 is located above the arcuate path 68, the openingof the switch blade 24 is not prevented by engagement therewith of thearcing tip 57.

When current flows through the hair pin shaped arcing horns 55-55,magnetic forces are produced which tend to move the shorter arms 56-56toward each other, thereby gripping the moving arcing tip 57 andmaintaining metal to metal contact as soon as possible after prestrikein air and until the ears 37 are in full contact engagement with thecontact surfaces of the inner arms 36-36 of the switch contact 28 whenthe switch blade 24 is swung to the completely closed position. Duringthe closing sequence of operations, the tie bar 64 provides a positivemember for providing a point of reaction for the magnetic forces actingto move the short arms 56-56 toward the arcing tip 57 and away from thelonger arms 58-58. The tie bar 64 also provides mechanical couplingbetween the longer arms 58-58 so that mechanical tuning fork vibrationsare not caused when the arcing tip 57 strikes the shorter arms 56-56with strictly mechanical metal to metal contact. Without the tie bar 64,if the arcing tip 57 should strike one of the shorter arms 56, it wouldtend to move away from the other shorter arm 56 since bight 70 is closeenough to the impact point to transmit the impact force to theassociated longer arm 58 which would then move about its lower endsupport in the boss 62. There would then be a tendency for the struckshorter arm 56 to move out of contact with the arcing tip 57 and asputtering arc to be drawn. When the longer arms 58-58 are connected bythe tie bar 64, such movement of the impacted arcing horn 55 isrestrained and the other arcing horn 55 is moved to maintain bothshorter arms 56-56 in contact with the arcing tip 57 without creation ofmechanical oscillations.

Damage incident to closing of the switch blade 24 against flow of highfault current is further minimized by moving it at high speed throughthe pre-strike are distance. This is accomplished by connecting anoperator to the linkage 17 that is capable of swinging the arcing tip 57through the pre-strike zone in a relatively short time of the order of0.1 second or less.

What is claimed as new is:

1. In a switch, in combination:

(a) a relatively stationary switch contact,

(b) a switch blade rotatably mounted at one end for swinging movementinto contact engagement with said switch contact,

(c) an arcing tip forming an extension of the distal end of said switchblade, and

(d) a pair of inverted U-shaped flexible arcing horns on opposite sidesof and engaging said arcing tip in the closed position of said switchblade,

(e) the arms of said arcing horns being of unequal length with thelonger arm of each pair attached to said switch contact and the shorterarm free to hex independently of the other shorter arm for engagementwith opposite sides of said arcing tip,

(f) said arcing horns being positioned in generally parallel planesintersecting said arcing tip generally at right angles with the shorterarms engaging said arcing tip in staggered relation,

(g) said shorter arms in the switch open position extending to oppositesides of the path of said arcing tip in moving to the switch closedposition.

2. The invention, as set forth in claim 1, wherein stop means limit themovement of the switch blade in the switch closing direction whereby thearcing tip is prevented from moving to a position below the distal endsof the shorter arms of the arcing horns.

3. In a switch, in combination:

(a) a relatively stationary switch contact,

(b) a switch blade rotatably mounted at one end for swinging movementinto contact engagement with said switch contact,

(c) an arcing tip forming an extension of the distal end of said switchblade, and

(d) a pair of inverted U-shaped flexible arcing horns on opposite sidesof and engaging said arching tip in the closed position of said switchblade,

(e) the arms of said arcing horns being of unequal length with thelonger arm of each pair attached to said switch contact and the shorterarm free to flex independently of the other shorter arm for engagementwith opposite sides of said arcing tip,

(f) said arcing horns being positioned in generally parallel planesintersecting said arcing tip generally at right angles with said shorterarms engaging said arcing tip in staggered relation,

(g) the coextensive portions of the arms of each arcing horn beinggenerally parallel in unstressed condition and inclined outwardly atacute angles away from the path of said arcing tip in moving to switchclosed position.

4. The invention, as set forth in claim 3, wherein the portions of thelonger arms immediately above the attachment to the switch contact aregenerally parallel to each other and the portions thereabove diverge atacute angles away from the plane of the path of the arcing tip.

5. In a switch, in combination:

(a) a relatively stationary switch contact,

(b) a switch blade rotatably mounted at one end for swinging movementinto contact engagement with said switch contact,

(c) an arching tip forming an extension of the distal end of said switchblade,

(d) a pair of inverted U-shaped flexible arching horns on opposite sidesof and engaging said arcing tip in the closed position of said switchblade,

(e) the arms of said arcing horns being of unequal length with thelonger arm of each pair attached to said switch contact to provideflexibility for said arcing horns to accommodate limited misalignment ofsaid arcing tip therewith and the shorter arm free to flex independentlyof the other shorter arm for engagement with opposite sides of saidarcing tip for good contact engagement therewith, and

(f) means spaced a substantial distance above the attachment of saidlonger arms to said switch contact and below the distal ends of saidshorter arms, said means rigidly interconnecting said longer arms andproviding a point of reaction for the magnetic forces on said shorterarms due to current flow therein and in said longer arms.

6. The invention, as set forth in claim 5, wherein the inverted U-shapedarcing horns are positioned in generally parallel planes intersectingthe arcing tip general ly at right angles with the shorter arms engagingsaid arcing tip in staggered relation.

7. The invention, as set forth in claim 6, wherein, when the switchblade is in the open position, the shorter arms of the arcing hornsextend to opposite sides of the path of the arcing tip in moving to theswitch closed position.

8. The invention, as set forth in claim '7, wherein stop means limit themovement of the switch blade in the switch closing direction whereby thearching tip is prevented from moving to a position below the distal endsof the shorter arms of the arcing horns.

9. The invention, as set forth in claim 6, wherein the arcuate path ofthe distal end of the arcing tip is below the eight of the arcing hornnearer the axis of rotation of the switch blade.

10. The invention, as set forth in claim 6, wherein:

(a) the coextensive portions of the arms of each arching horn aregenerally parallel, and

(b) they are inclined outwardly at actue angles away from the path ofthe arcing tip in moving to the switch closed position.

11. The invention, as set forth in claim 10, wherein the portions of thelonger arms immediately above the attachment to the switch contact aregenerally parallel to each other and the portions thereabove diverge atacute angles away from the plane of the path of the arcing tip.

12. In a switch, in combination:

(a) a relatively stationary switch contact,

(b) a switch blade rotatably mounted at one end for swinging movementinto contact engagement with said switch contact,

(c) an arcing tip forming an extension of the distal end of said switchblade,

(d) a pair of inverted U-shaped flexible arcing horns on opposite sidesof and engaging said arcing tip in the closed position of said switchblade,

(e) the arms of said arcing horns being of unequal length with thelonger arms of each pair attached to said switch contact and the shorterarm free to flex independently of the other shorter arm for engagementwith opposite sides of said arcing tip, and

(f) means spaced a substantial distance above the attachment of saidlonger arms to said switch contact and below the distal ends of saidshorter arms, said means rigidly interconnecting said longer arms andcomprising a tie bar extending transversely of said longer arms andsecured at its ends thereto.

13. The invention, as set forth in claim 12, wherein:

(a) the arcing horns are formed of rod-like resilient material having acircular cross section,

(b) the tie bar has a transversely extending circular opening near eachend for receiving therethrough the respective longer arm, and

(c) means cooperate with said tie bar and the longer arms to hold theformer in position on the latter.

14. The invention, as set forth in claim 12, wherein,

when the switch blade is in the open position, the shorter arms of thearcing horns extend to opposite sides of the path of the arcing tip inmoving to the switch closed position.

15. The invention, as set forth in claim 12, wherein:

(a) the coextensive portions of the arms of each arcing horn aregenerally parallel, and

(b) they are inclined outwardly at acute angles away form the path ofthe arcing tip in moving to the switch closed position.

References Cited by the Examiner UNITED STATES PATENTS 2,313,771 3/43Rossman 200-l62 2,555,588 6/51 Gussow 200146 2,894,101 7/59 Lindell etal. 200170 3,144,536 8/64 Bridges et a1. 200146 KATHLEEN H. CLAFFY,Primary Examiner.

BERNARD A. GILHEANY, Examiner.

IINITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,206,581 September 14, l'J-ES John J. Mikos It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 6, line 59, and column 7, line 14 and lines 22 and 23, for"arching", each occurrence, read arcing column 7, line 24, for "actue"read acute column 8, line 29, for "form" read from Signed and sealedthis 5th day of April 1966.

EAL)

NEST W. SWIDER EDWARD J. BRENNER esting Officer Commissioner of Patents

5. IN A SWITCH, IN COMBINATION: (A) A RELATIVELY STATIONARY SWITCHCONTACT, (B) A SWITCH BLADE ROTATABLY MOUNTED AT ONE END FOR SWINGINGMOVEMENT INTO CONTACT ENGAGEMENT WITH SAID SWITCH CONTACT, (C) ANARCHING TIP FORMING AN EXTENSION OF THE DISTAL END OF SAID SWITCH BLADE,(D) A PAIR OF INVERTED U-SHAPED FLEXIBLE ARCHING HORNS ON OPPOSITE SIDESOF AND ENGAGING SAID ARCING TIP IN THE CLOSED POSITION OF SAID SWITCHBLADE, (E) THE ARMS OF SAID ARCING HORNS BEING OF UNEQUAL LENGTH WITHTHE LONGER ARM OF EACH PAIR ATTACHED TO SAID SWITCH CONTACT TO PROVIDEFLEXIBILITY FOR SAID ARCING HORNS TO ACCOMMODATE LIMITED MISALIGNMENT OFSAID ARCING TIP THEREWITH AND THE SHORTER ARM FREE TO FLEX INDEPENDENTLYOF THE OTHER SHORTER ARM FOR ENGAGEMENT WITH OPPOSITE SIDES OF SAIDARCING TIP FOR GOOD CONTACT ENGAGEMENT THEREWITH, AND (F) MEANS SPACED ASUBSTANTAIL DISTANCE ABOVE THE ATTACHMENT OF SAID LONGER ARMS TO SAIDSWITCH CONTACT AND BELOW THE DISTAN ENDS OF SAID SHORTER ARMS, SAIDMEANS RIGIDLY INTERCONNECTING SAID LONGER ARMS AND PROVIDING A POINT OFREACTION FOR THE MAGNETIC FORCES ON SAID SHORTER ARMS DUE TO CURRENTFLOW THEREIN AND IN SAID LONGER ARMS.